The recent proliferation of wireless telecommunications has led many subscribers to become more and more reliant on their mobile devices. For some users, it is important to remain reliably accessible via their mobile phones so that family, business contacts, and clients can reach them at a moment's notice. Nevertheless, users may be unable to access their mobile phone in some circumstances, and may consequently miss a call relating to an important issue, such as a family emergency or a professional obligation requiring the user's immediate attention.